International Docking Adapter

Photo: NASA

The International Docking Adapters (IDAs) will be installed on Pressurized Mating Adapters 2 and 3 of the International Space Station to convert the APAS-95 docking interface used by the Space Shuttle to the NASA Docking System that is compatible with the International Docking System Standard.

The IDAs are compatible with the NASA Docking System which is an androgynous design supporting low-impact technology. Automated and piloted Spacecraft docking and robotic spacecraft berthing will be possible with the NDS. The docking interface includes architecture to transfer data and power between the two vehicles with future systems also capable of propellant, pressurant and water transfers. The hatch diameter available to crews is 80 centimeters.

Image: NASA

For a docking, one interface is in active mode with its Soft Capture System extended while the other spacecraft is in a passive role with its SCS in a stowed position.

The Docking System includes a Soft Capture System that forms the initial connection between the spacecraft before pulling the two docking systems together to allow the Hard Capture System to form a rigid seal between the two spacecraft. Hooks are available on the active and passive side of the docking system, providing up to 24 attachment points. Overall, the system consists of a capture ring, guide petals, soft docking magnets, mechanical latches, magnetic striker plates, latch strikers and sensor strikers. The strikers are part of the passive system and provide contact surfaces for components of the active system. Soft capture can be achieved using magnetic or mechanical soft capture latches.

Image: NASA

The first elements to make contact are the guide petals that then correct any lateral or angular misalignment between the docking interfaces with soft capture being achieved either through magnets making contact with the striker plates on the opposing ring or through active latches that capture passive latch strikers to from a soft-mate.

The SCS then aligns the two docking rings and through the retraction of SCS, the two Hard Capture Interfaces are positioned within their hard capture range to allow fine alignment by the HCS guide pins.

Hooks are then used on either the active, passive or both sides to establish the structural connection between the spacecraft and achieving the required force to press the seals within the docking system against the other spacecraft. Each side includes 12 hooks – the passive and active hooks can both be closed if dictated by vehicle requirements.

Due to the low force required for a Soft Capture, the NDS can support robotic berthing of a spacecraft.